Laminated LC filter

ABSTRACT

In a laminated LC filter, at least four LC parallel resonators are provided inside a multilayer body. At least a pair of loops of inductors in odd numbered-stage LC parallel resonators among the at least four LC parallel resonators are disposed at an angle at which magnetic coupling is obtained therebetween, and winding directions thereof are the same, so as to obtain magnetic coupling between the inductors. In addition, magnetic coupling may also be obtained between a pair of loops of inductors in even numbered-staged LC parallel resonators among the at least four LC parallel resonators.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application 2015-189058 filed Sep. 26, 2015. The entire contents of this application are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to laminated LC filters, and specifically relates to a laminated LC filter that has a wide pass band and an attenuation pole with sufficient attenuation near the pass band.

2. Description of the Related Art

As an LC filter that is suitable to achieve miniaturization and weight-saving and has excellent characteristics, a laminated LC filter is widely used in which LC parallel resonators defined by inductors and capacitors are configured in a multistage configuration inside a multilayer body where a plurality of dielectric layers are laminated; the inductors and capacitors of the LC parallel resonators are provided in the multilayer body using line electrodes, capacitor electrodes, ground electrodes, and via electrodes.

Laminated LC filters are required to have optimum frequency characteristics in accordance with desired usage thereof.

As such a laminated LC filter, a laminated LC filter (laminated band pass filter) is disclosed in International Publication No. WO 2012/077498.

FIG. 7 illustrates a laminated LC filter 1100 disclosed in International Publication No. WO 2012/077498. FIG. 7 is an exploded perspective view of the laminated LC filter 1100. FIG. 8 is an equivalent circuit diagram of the laminated LC filter 1100.

The laminated LC filter 1100 includes a multilayer body 101 in which 15 layers of dielectric layers 101 a through 101 o are laminated in sequence from the bottom to the top.

Input-output terminals (input terminals) 102 a and 102 b are respectively provided on both end surfaces of the dielectric layer 101 a. Further, capacitor electrodes 103 a and 103 b and a ground electrode (earth electrode) 104 a are provided on an upper-side main surface of the dielectric layer 101 a. The capacitor electrode 103 a is connected to the input-output terminal 102 a and the capacitor electrode 103 b is connected to the input-output terminal 102 b.

Although not shown in FIG. 7, one end of each of the input-output terminals 102 a and 102 b extends to a lower-side main surface of the dielectric layer 101 a.

The input-output terminals 102 a and 102 b are also provided on both end surfaces of each of the dielectric layers 101 b through 101 o to be explained later. However, to simplify the drawings and the explanation thereof, assignment of reference signs in the drawings and description in the specification are omitted in some cases.

Capacitor electrodes 103 c and 103 d are provided on an upper-side main surface of the dielectric layer 101 b. Further, via electrodes 105 a and 105 b extend through both of the main surfaces of the dielectric layer 101 b. The capacitor electrode 103 c is connected to the input-output terminal 102 a and the capacitor electrode 103 d is connected to the input-output terminal 102 b. The via electrodes 105 a and 105 b are both connected to the ground electrode 104 a.

A ground electrode 104 b is provided on an upper-side main surface of the dielectric layer 101 c. In addition, via electrodes 105 c and 105 d extend through both of the main surfaces of the dielectric layer 101 c. The ground electrode 104 b is connected to the via electrodes 105 c and 105 d. Further, the via electrode 105 c is connected to the via electrode 105 a and the via electrode 105 d is connected to the via electrode 105 b.

Capacitor electrodes 103 e and 103 f are provided on an upper-side main surface of the dielectric layer 101 d. In addition, six via electrodes 105 e through 105 j extend through both of the main surfaces of the dielectric layer 101 d. The capacitor electrode 103 e is connected to the input-output terminal 102 a and the capacitor electrode 103 f is connected to the input-output terminal 102 b. The six via electrodes 105 e through 105 j are all connected to the ground electrode 104 b.

A capacitor electrode 103 g is provided on an upper-side main surface of the dielectric layer 101 e. In addition, six via electrodes 105 k through 105 p extend through both of the main surfaces of the dielectric layer 101 e. The via electrode 105 k is connected to the via electrode 105 e, the via electrode 105 l is connected to the via electrode 105 f, the via electrode 105 m is connected to the via electrode 105 g, the via electrode 105 n is connected to the via electrode 105 h, the via electrode 105 o is connected to the via electrode 105 i, and the via electrode 105 p is connected to the via electrode 105 j.

Capacitor electrodes 103 h and 103 i are provided on an upper-side main surface of the dielectric layer 101 f. In addition, six via electrodes 105 q through 105 v extend through both of the main surfaces of the dielectric layer 101 f. The capacitor electrode 103 h is connected to the input-output terminal 102 a and the capacitor electrode 103 i is connected to the input-output terminal 102 b. Further, the via electrode 105 q is connected to the via electrode 105 k, the via electrode 105 r is connected to the via electrode 105 l, the via electrode 105 s is connected to the via electrode 105 m, the via electrode 105 t is connected to the via electrode 105 n, the via electrode 105 u is connected to the via electrode 105 o, and the via electrode 105 v is connected to the via electrode 105 p.

A ground electrode 104 c is provided on an upper-side main surface of the dielectric layer 101 g. In addition, six via electrodes 105 w through 105 ab extend through both of the main surfaces of the dielectric layer 101 g. The ground electrode 104 c is connected to the six via electrodes 105 w through 105 ab. Further, the via electrode 105 w is connected to the via electrode 105 q, the via electrode 105 x is connected to the via electrode 105 r, the via electrode 105 y is connected to the via electrode 105 s, the via electrode 105 z is connected to the via electrode 105 t, the via electrode 105 aa is connected to the via electrode 105 u, and the via electrode 105 ab is connected to the via electrode 105 v.

In this specification, when reference signs are assigned to certain constituent elements, where the number of the stated constituent elements is no more than 26, alphabetical letters “a” through “z” are used; where the number thereof exceeds 26, combinations of an alphabetical letter “a” and alphabetical letters “a” through “z” are used; where the number thereof further exceeds another 26, combinations of an alphabetical letter “b” and alphabetical letters “a” through “z” are used. For example, a total of 69 via electrodes are provided in the laminated LC filter 1100, and these via electrodes are represented by using reference signs 105 a through 105 z, 105 aa through 105 az, and 105 ba through 105 bu, respectively.

Capacitor electrodes 103 j and 103 k are provided on an upper-side main surface of the dielectric layer 101 h. Further, five via electrodes 105 ac through 105 ag extend through both of the main surfaces of the dielectric layer 101 h. The five via electrodes 105 ac through 105 ag are all connected to the ground electrode 104 c.

Capacitor electrodes 103 l and 103 m are provided on an upper-side main surface of the dielectric layer 101 i. In addition, seven via electrodes 105 ah through 105 an extend through both of the main surfaces of the dielectric layer 101 i. The capacitor electrode 103 l is connected to the via electrode 105 aj and the capacitor electrode 103 m is connected to the via electrode 105 al. Further, the via electrode 105 ah is connected to the capacitor electrode 103 j, the via electrode 105 ai is connected to the via electrode 105 ac, the via electrode 105 aj is connected to the via electrode 105 ad, the via electrode 105 ak is connected to the via electrode 105 ae, the via electrode 105 al is connected to the via electrode 105 af, the via electrode 105 am is connected to the via electrode 105 ag, and the via electrode 105 an is connected to the capacitor electrode 103 k.

Capacitor electrodes 103 n and 103 o are provided on an upper-side main surface of the dielectric layer 101 j. In addition, five via electrodes 105 ao through 105 as extend through both of the main surfaces of the dielectric layer 101 j. The capacitor electrode 103 n is connected to the via electrode 105 ao and the capacitor electrode 103 o is connected to the via electrode 105 as. Further, the via electrode 105 ao is connected to the via electrode 105 ah, the via electrode 105 ap is connected to the via electrode 105 ai, the via electrode 105 aq is connected to the via electrode 105 ak, the via electrode 105 ar is connected to the via electrode 105 am, and the via electrode 105 as is connected to the via electrode 105 an.

Line electrodes 106 a and 106 b are provided on an upper-side main surface of the dielectric layer 101 k. Further, five via electrodes 105 at through 105 ax extend through both of the main surfaces of the dielectric layer 101 k. One end of the line electrode 106 a is connected to the input-output terminal 102 a and one end of the line electrode 106 b is connected to the input-output terminal 102 b. The via electrode 105 at is connected to the capacitor electrode 103 n, the via electrode 105 au is connected to the via electrode 105 ap, the via electrode 105 av is connected to the via electrode 105 aq, the via electrode 105 aw is connected to the via electrode 105 ar, and the via electrode 105 ax is connected to the capacitor electrode 103 o.

Line electrodes 106 c and 106 d are provided on an upper-side main surface of the dielectric layer 1011. Further, seven via electrodes 105 ay through 105 be extend through both of the main surfaces of the dielectric layer 101 l. One end of the line electrode 106 c and one end of the line electrode 106 d are both connected to the via electrode 105 bb. The via electrode 105 ay is connected to the other end of the line electrode 106 a, the via electrode 105 az is connected to the via electrode 105 at, the via electrode 105 ba is connected to the via electrode 105 au, the via electrode 105 bb is connected to the via electrode 105 av, the via electrode 105 bc is connected to the via electrode 105 aw, the via electrode 105 bd is connected to the via electrode 105 ax, and the via electrode 105 be is connected to the other end of the line electrode 106 b.

Four line electrodes 106 e through 106 h are provided on an upper-side main surface of the dielectric layer 101 m. In addition, eight via electrodes 105 bf through 105 bm extend through both of the main surfaces of the dielectric layer 101 m. One end of the line electrode 106 e is connected to the via electrode 105 bf, the other end of the line electrode 106 e is connected to the via electrode 105 bj, one end of the line electrode 106 f is connected to the via electrode 105 bg, the other end of the line electrode 106 f is connected to the via electrode 105 bi, one end of the line electrode 106 g is connected to the via electrode 105 bj, the other end of the line electrode 106 g is connected to the via electrode 105 b 1, one end of the line electrode 106 h is connected to the via electrode 105 bk, and the other end of the line electrode 106 h is connected to the via electrode 105 bm. Further, the via electrode 105 bf is connected to the via electrode 105 ay, the via electrode 105 bg is connected to the via electrode 105 az, the via electrode 105 bh is connected to the via electrode 105 ba, the via electrode 105 bi is connected to the other end of the line electrode 106 c, the via electrode 105 bj is connected to the other end of the line electrode 106 d, the via electrode 105 bk is connected to the via electrode 105 bc, the via electrode 105 b 1 is connected to the via electrode 105 bd, and the via electrode 105 bm is connected to the via electrode 105 be.

Four line electrodes 106 i through 106 l are provided on an upper-side main surface of the dielectric layer 101 n. In addition, eight via electrodes 105 bn through 105 bu extend through both of the main surfaces of the dielectric layer 101 n. One end of the line electrode 106 i is connected to the via electrode 105 bn, the other end of the line electrode 106 i is connected to the via electrode 105 bp, one end of the line electrode 106 j is connected to the via electrode 105 bo, the other end of the line electrode 106 j is connected to the via electrode 105 bq, one end of the line electrode 106 k is connected to the via electrode 105 br, the other end of the line electrode 106 k is connected to the via electrode 105 bt, one end of the line electrode 106 l is connected to the via electrode 105 bs, and the other end of the line electrode 106 l is connected to the via electrode 105 bu. Further, the via electrode 105 bn is connected to the one end of the line electrode 106 e, the via electrode 105 bo is connected to the one end of the line electrode 106 f, the via electrode 105 bp is connected to the other end of the line electrode 106 e, the via electrode 105 bq is connected to the other end of the line electrode 106 f, the via electrode 105 br is connected to the one end of the line electrode 106 g, the via electrode 105 bs is connected to the one end of the line electrode 106 l, the via electrode 105 bt is connected to the other end of the line electrode 106 g, and the via electrode 105 bu is connected to the other end of the line electrode 106 h.

The input-output terminals 102 a and 102 b are provided on both end surfaces of the dielectric layer 101 o. One end of each of the input-output terminals 102 a and 102 b extends to an upper-side main surface of the dielectric layer 101 o.

As discussed above, in the laminated LC filter 1100, the input-output terminals 102 a and 102 b are provided on the surface of the multilayer body 101. Inside the multilayer body 101, the capacitor electrodes 103 a through 103 o, the ground electrodes 104 a through 104 c, the via electrodes 105 a through 105 bu, and the line electrodes 106 a through 106 l are provided.

The laminated LC filter 1100 disclosed in International Publication No. WO 2012/077498 has the above-discussed structure and has an equivalent circuit as shown in FIG. 8.

The laminated LC filter 1100 is configured such that four LC parallel resonators Re1 through Re4 are inserted between the ground and a signal line connecting the input-output terminals 102 a and 102 b.

An inductor L1 and a capacitor C1 are connected in parallel in the first-stage LC parallel resonator Re1.

An inductor L2 and a capacitor C2 are connected in parallel in the second-stage LC parallel resonator Re2.

An inductor L3 and a capacitor C3 are connected in parallel in the third-stage LC parallel resonator Re3.

An inductor L4 and a capacitor C4 are connected in parallel in the fourth-stage LC parallel resonator Re4.

Note that the inductor L2 in the second-stage LC parallel resonator Re2 and the inductor L3 in the third-stage LC parallel resonator Re3 are connected to each other and then connected to the ground through a common inductor L23.

A capacitor C14 is connected, in parallel to the signal line, between the input-output terminals 102 a and 102 b.

With reference to FIGS. 7 and 8, a relationship between the structure and the equivalent circuit of the laminated LC filter 1100 will be described next.

In a laminated LC filter, to improve a Q value, multi-layered line electrodes having a plurality of layers are provided in some cases. As such, in the laminated LC filter 1100, the one end of the line electrode 106 e and the one end of the line electrode 106 i are connected through the via electrode 105 bn while the other ends thereof are connected through the via electrode 105 bp, such that the line electrodes 106 e and 106 i are multi-layered. Similarly, the one end of the line electrode 106 f and the one end of the line electrode 106 j are connected with the via electrode 105 bo while the other ends thereof are connected through the via electrode 105 bq, such that the line electrodes 106 f and 106 j are multi-layered. Further, the one end of the line electrode 106 g and the one end of the line electrode 106 k are connected through the via electrode 105 br while the other ends thereof are connected through the via electrode 105 bt, such that the line electrodes 106 g and 106 k are multi-layered. Furthermore, the one end of the line electrode 106 h and the one end of the line electrode 106 l are connected through the via electrode 105 bs while the other ends thereof are connected through the via electrode 105 bu, such that the line electrodes 106 h and 106 l are multi-layered.

The inductor L1 in the first-stage LC parallel resonator Re1 is defined by a loop connecting the input-output terminal 102 a, the line electrode 106 a, the via electrode 105 ay, the via electrode 105 bf, the line electrode 106 e and the line electrode 106 i that are connected to one another through the via electrode 105 bn and the via electrode 105 bp, the via electrode 105 bh, the via electrode 105 ba, the via electrode 105 au, the via electrode 105 ap, the via electrode 105 ai, the via electrode 105 ac, and the ground electrode 104 c.

The capacitor C1 in the first-stage LC parallel resonator Re1 is primarily defined by a capacitance produced between the ground electrode 104 b and the capacitor electrodes 103 c and 103 e, and a capacitance produced between the capacitor electrode 103 h and the ground electrode 104 c. The capacitor electrodes 103 c, 103 e, and 103 h are all connected to the input-output terminal 102 a.

The inductor L1 and the capacitor C1 in the first-stage LC parallel resonator Re1 are not directly connected to one another, but are indirectly connected through the input-output terminal 102 a.

The inductor L2 in the second-stage LC parallel resonator Re2 is defined by a loop connecting the capacitor electrode 103 j and capacitor electrode 103 n connected to each other through the via electrode 105 ah and via electrode 105 ao, the via electrode 105 at, the via electrode 105 az, the via electrode 105 bg, the line electrode 106 e and the line electrode 106 i connected to one another through the via electrode 105 bo and the via electrode 105 bq, the via electrode 105 bi, and the line electrode 106 c.

The capacitor C2 in the second-stage LC parallel resonator Re2 is primarily defined by a capacitance produced between the capacitor electrodes 103 j and 103 n, and the ground electrode 104 c and the capacitor electrode 103 l. Note that the capacitor electrodes 103 j and 103 n are connected through the via electrodes 105 ah and 105 ao as discussed above. Further, the capacitor electrode 103 l is connected to the ground electrode 104 c through the via electrodes 105 aj and 105 ad.

The inductor L3 in the third-stage LC parallel resonator Re3 is defined by a loop connecting the capacitor electrode 103 k and capacitor electrode 103 o connected to each other through the via electrode 105 an and via electrode 105 as, the via electrode 105 ax, the via electrode 105 bd, the via electrode 105 b 1, the line electrode 106 g and line electrode 106 k are connected to one another through the via electrode 105 br and via electrode 105 bt, the via electrode 105 bj, and the line electrode 106 d.

The capacitor C3 in the third-stage LC parallel resonator Re3 is primarily defined by a capacitance produced between the capacitor electrodes 103 k and 103 o, and the ground electrode 104 c and the capacitor electrode 103 m. Note that the capacitor electrodes 103 k and 103 o are connected through the via electrodes 105 an and 105 as as discussed above. Further, the capacitor electrode 103 m is connected to the ground electrode 104 c through the via electrodes 105 al and 105 af.

The inductor L4 in the fourth-stage LC parallel resonator Re4 is defined by a loop connecting the input-output terminal 102 b, the line electrode 106 b, the via electrode 105 be, the via electrode 105 bm, the line electrode 106 h and line electrode 106 l connected to each other through the via electrode 105 bs and via electrode 105 bu, the via electrode 105 bk, the via electrode 105 bc, the via electrode 105 aw, the via electrode 105 ar, the via electrode 105 am, the via electrode 105 ag, and the ground electrode 104 c.

The capacitor C4 in the fourth-stage LC parallel resonator Re4 is primarily defined by a capacitance produced between the ground electrode 104 b and the capacitor electrodes 103 d and 103 f, and a capacitance produced between the capacitor electrode 103 i and the ground electrode 104 c. Note that the capacitor electrodes 103 d, 103 f, and 103 i are all connected to the input-output terminal 102 a.

The inductor L4 and the capacitor C4 in the fourth-stage LC parallel resonator Re4 are not directly connected, but are indirectly connected through the input-output terminal 102 b.

As discussed above, the inductor L2 in the second-stage LC parallel resonator Re2 and the inductor L3 in the third-stage LC parallel resonator Re3 are connected to each other and then connected to the ground through the common inductor L23. The common inductor L23 is defined by a path connecting the via electrodes 105 bb, 105 av, 105 aq, 105 ak, and 105 ae, and is connected to the ground electrode 104 c. Note that the common inductor L23 can be considered to be a portion of the inductor L2 in the second-stage LC parallel resonator Re2 and also a portion of the inductor L3 in the third-stage LC parallel resonator Re3.

The capacitor C14 is primarily defined by a capacitance produced by the capacitor electrodes 103 e and 103 h, the capacitor electrode 103 g as a floating electrode, and the capacitor electrodes 103 f and 103 i.

In the laminated LC filter 1100, the loop of the inductor L1 in the first-stage LC parallel resonator Re1 and the loop of the inductor L2 in the second-stage LC parallel resonator Re2 are disposed in parallel, and the winding directions thereof are the same. As such, the inductor L1 and the inductor L2 are coupled by magnetic coupling M12.

Similarly, the loop of the inductor L3 in the third-stage LC parallel resonator Re3 and the loop of the inductor L4 in the fourth-stage LC parallel resonator Re4 are disposed in parallel, and the winding directions thereof are the same. As such, the inductor L3 and the inductor L4 are coupled by magnetic coupling M34.

The loop of the inductor L2 in the second-stage LC parallel resonator Re2 and the loop of the inductor L3 in the third-stage LC parallel resonator Re3 are parallel to each other, but are obliquely disposed and the winding directions thereof are different from each other. Therefore, the strength of magnetic coupling therebetween is weak. As such, in the laminated LC filter 1100, the inductor L2 and the inductor L3 are connected to each other and then connected to the ground through the common inductor L23, so as to obtain magnetic coupling M23 between the inductor L2 and the inductor L3.

Detailed description about this will be provided below. That is, in the laminated LC filter 1100, an attenuation pole is provided near the pass band by making the winding direction of the loop of the inductor L2 and the winding direction of the loop of the inductor L3 to differ from each other, so as to make it possible to obtain high attenuation characteristics. However, when the winding direction of the loop of the inductor L2 and the winding direction of the loop of the inductor L3 are different, the strength of magnetic coupling between the inductor L2 and the inductor L3 is weak and, consequently, the pass band is narrowed. As such, in the laminated LC filter 1100, as discussed above, the inductors L2 and L3 are connected to each other and then connected to the ground through the common inductor L23, such that the magnetic coupling M23 between the inductors L2 and L3 is strengthened and the pass band is widened.

The first-stage LC parallel resonator Re1 and the fourth-stage LC parallel resonator Re4 are capacitively coupled through the capacitor C14, that is, coupled to each other while bypassing the other LC parallel resonators.

FIG. 9 illustrates frequency characteristics of the laminated LC filter 1100 disclosed in International Publication No. WO 2012/077498.

In the laminated LC filter 1100 disclosed in International Publication No. WO 2012/077498, the inductors L2 and L3 are connected to each other and then connected to the ground through the common inductor L23 as shown in FIG. 8, such that the magnetic coupling M23 between the inductors L2 and L3 is strengthened and the pass band is widened as shown in FIG. 9.

However, in the laminated LC filter 1100, because the inductors L2 and L3 are connected to each other and then connected to the ground through the common inductor L23, attenuation of attenuation poles near the pass band, especially attenuation of the attenuation pole on a higher frequency side of the pass band is insufficient, as shown in FIG. 9, so that high attenuation characteristics cannot be obtained.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide a laminated LC filter that has high attenuation characteristics by providing an attenuation pole with sufficient attenuation near a pass band, so as to overcome the above-mentioned problem while maintaining a wide pass band.

A laminated LC filter according to a preferred embodiment of the present invention includes a multilayer body in which a plurality of dielectric layers are laminated; a plurality of line electrodes laminated between layers in the plurality of dielectric layers; a plurality of capacitor electrodes laminated between layers in the plurality of dielectric layers; at least one ground electrode laminated between layers in the plurality of dielectric layers; and a plurality of via electrodes extending through both main surfaces of layers in the plurality of dielectric layers. At least four LC parallel resonators are provided inside the multilayer body. An inductor and a capacitor are connected in parallel in each of the LC parallel resonators. The inductor is defined by a capacitor-side via electrode portion which includes at least one via electrode and one end of which is connected to a capacitor electrode, a line electrode portion which includes at least one line electrode and one end of which is connected to the other end of the capacitor-side via electrode portion, and a ground-side via electrode portion which includes at least one via electrode, one end of which is connected to the other end of the line electrode portion, and the other end of which is connected to the ground electrode. Further, the inductor includes a loop having a predetermined winding direction and connecting the capacitor-side via electrode portion, the line electrode portion, and the ground-side via electrode portion. The capacitor is defined by a capacitance produced between the capacitor electrode and the ground electrode or a capacitance produced among the plurality of capacitor electrodes. The loops of the inductors of at least a pair of the LC parallel resonators in at least one of a pair of odd numbered-stage LC parallel resonators and a pair of even numbered-stage LC parallel resonators among at least the four LC parallel resonators are disposed at an angle at which magnetic coupling is obtained between each other, and winding directions of the loops of the inductors are the same. The pair of loops which are disposed at an angle at which magnetic coupling is obtained between each other and whose winding directions are the same refers to the loop of the inductor in the first-stage LC parallel resonator and the loop of the inductor in the third-stage LC parallel resonator, or the loop of the inductor in the second-stage LC parallel resonator and the loop of the inductor in the fourth-stage LC parallel resonator. The winding directions of the loop of the inductor in the second-stage LC parallel resonator and the loop of the inductor in the third-stage LC parallel resonator are different from each other. The ground-side via electrode portion of the inductor in the second-stage LC parallel resonator and the ground-side via electrode portion of the inductor in the third-stage LC parallel resonator are integrated so as to define a common ground-side via portion, and the common ground-side via portion is connected to the ground electrode.

The inductor loops of the inductors in the first-stage and third-stage LC parallel resonators as well as the inductor loops of the inductors in the second-stage and fourth-stage LC parallel resonators may preferably be each disposed at an angle at which magnetic coupling is obtained between each other and the winding directions thereof may be the same. In this case, an attenuation pole having further improved attenuation is provided near the pass band, particularly on a higher frequency side relative to the pass band, thus making it possible to obtain high attenuation characteristics.

The line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator may preferably each be multi-layered and include a plurality of layers of the line electrode portion, and the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator may preferably be directly connected or connected through the line electrode in each layer. Alternatively, the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator may preferably each be a single-layered line electrode portion, and the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator may preferably be directly connected or connected through the line electrode. In these cases, the magnetic coupling between the inductor in the second-stage LC parallel resonator and the inductor in the third-stage LC parallel resonator is further strengthened as compared to when the inductor in the second-stage LC parallel resonator and the inductor in the third-stage LC parallel resonator are integrated to be at least partially common halfway and connected to the ground, so as to further widen the pass band.

Of the two examples of preferred embodiments of the present invention described above, when the line electrode portions of the inductors are each multi-layered and include a plurality of layers, an improved Q value of the inductor is also achieved.

According to a laminated LC filter of a preferred embodiment of the present invention, an attenuation pole having sufficient attenuation is provided near a pass band while maintaining a wide pass band, such that high attenuation characteristics is obtained.

More specifically, at least a pair of inductor loops in at least one of a pair of odd numbered-stage LC parallel resonators and a pair of even numbered-stage LC parallel resonators is disposed at an angle at which magnetic coupling is obtained between each other, and winding directions of the inductor loops are the same. This makes it possible for the inductors in the LC parallel resonators to be strongly magnetically coupled to each other. As a result, an attenuation pole having sufficient attenuation is provided near the pass band, specifically on a higher frequency side relative to the pass band, so that high attenuation characteristics are obtained.

Further, the ground-side via electrode portion of the inductor in the second-stage LC parallel resonator and the ground-side via electrode portion of the inductor in the third-stage LC parallel resonator are integrated to define the common ground-side via portion, and the common ground-side via portion is connected to the ground electrode. As such, although the winding direction of the inductor loop in the second-stage LC parallel resonator is opposite to the winding direction of the inductor loop of the third-stage LC parallel resonator, the inductor in the second-stage LC parallel resonator and the inductor in the third-stage LC parallel resonator are magnetically coupled, thereby widening the pass band.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view illustrating a laminated LC filter 100 according to a first preferred embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the laminated LC filter 100.

FIG. 3 is a graph illustrating frequency characteristics of the laminated LC filter 100.

FIG. 4 is an exploded perspective view illustrating a main portion of a laminated LC filter 200 according to a second preferred embodiment of the present invention, and the laminated LC filter 100 according to the first preferred embodiment of the present invention is also illustrated in FIG. 4 for reference.

FIG. 5 is an exploded perspective view illustrating a main portion of a laminated LC filter 300 according to a third preferred embodiment of the present invention, and the laminated LC filter 100 according to the first preferred embodiment of the present invention is also illustrated in FIG. 5 for reference.

FIG. 6 is an exploded perspective view illustrating a laminated LC filter 400 according to a fourth preferred embodiment of the present invention.

FIG. 7 is an exploded perspective view illustrating a laminated LC filter 1100 disclosed in International Publication No. WO 2012/077498.

FIG. 8 is an equivalent circuit diagram of the laminated LC filter 1100.

FIG. 9 is a graph illustrating frequency characteristics of the laminated LC filter 1100.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

The preferred embodiments described herein are merely examples, and therefore the present invention is not limited to the contents of the preferred embodiments in any way. Further, contents described in the different preferred embodiments can be combined with one another. In this case, the combined contents of such a preferred embodiment are also included in the present invention. It is to be noted that the drawings are prepared to facilitate the understanding of the preferred embodiments and are not precisely illustrated in some cases. For example, there is a case in which dimensional ratios of the illustrated constituent elements or dimensional ratios between the illustrated constituent elements are not equal to those described in the specification. Further, there are cases in which constituent elements illustrated in the specification are omitted in the drawings, a smaller number of constituent elements than an actual number thereof are illustrated in the drawings, and other differences.

First Preferred Embodiment

A laminated LC filter 100 according to a first preferred embodiment of the present invention is shown in FIGS. 1 and 2. FIG. 1 is an exploded perspective view of the laminated LC filter 100. FIG. 2 is an equivalent circuit diagram of the laminated LC filter 100.

The laminated LC filter 100 includes a multilayer body 1 in which dielectric layers 1 a through 1 k are laminated in eleven layers, for example, in sequence from the bottom to the top. Ceramics are preferably used for the multilayer body 1 (dielectric layers 1 a-1 k), for example.

A pair of input-output terminals 2 a and 2 b are provided on end surfaces of the dielectric layer 1 a that oppose each other. Ground terminals 3 a and 3 b are provided on side surfaces of the dielectric layer 1 a that oppose each other.

Connection electrodes 4 a, 4 b and a ground electrode 5 a are provided on an upper-side main surface of the dielectric layer 1 a. The connection electrode 4 a is connected to the input-output terminal 2 a and the connection electrode 4 b is connected to the input-output terminal 2 b. The ground electrode 5 a is connected to both of the ground terminals 3 a and 3 b.

One end of each of the input-output terminals 2 a, 2 b and the ground terminals 3 a, 3 b extends to a lower-side main surface of the dielectric layer 1 a.

The input-output terminals 2 a, 2 b and the ground terminals 3 a, 3 b are also provided on end surfaces and side surfaces, respectively, of the dielectric layers 1 b through 1 k as will be explained below. However, in order to facilitate understanding of the drawings and to simplify the explanation thereof, the assignment of reference signs in the drawings and the description thereof in the specification are omitted in some cases.

Line electrodes 6 a and 6 b are provided on an upper-side main surface of the dielectric layer 1 b. Further, four via electrodes 7 a through 7 d extend through both of the main surfaces of the dielectric layer 1 b. One end of the line electrode 6 a is connected to the via electrode 7 a and one end of the line electrode 6 b is connected to the via electrode 7 d. Further, the via electrode 7 a is connected to the connection electrode 4 a and the via electrode 7 d is connected to the connection electrode 4 b. The via electrodes 7 b and 7 c are both connected to the ground electrode 5 a.

Line electrodes 6 c, 6 d and a capacitor electrode 8 a are provided on an upper-side main surface of the dielectric layer 1 c. Six via electrodes 7 e through 7 j extend through both of the main surfaces of the dielectric layer 1 c. One end of the line electrode 6 c is connected to the via electrode 7 f, the other end of the line electrode 6 c is connected to the via electrode 7 e, one end of the line electrode 6 d is connected to the via electrode 7 i, and the other end of the line electrode 6 d is connected to the via electrode 7 j. Further, the via electrode 7 f is connected to the one end of the line electrode 6 a, the via electrode 7 e is connected to the other end of the line electrode 6 a, the via electrode 7 g is connected to the via electrode 7 b, the via electrode 7 h is connected to the via electrode 7 c, the via electrode 7 i is connected to the one end of the line electrode 6 b, and the via electrode 7 j is connected to the other end of the line electrode 6 b.

Capacitor electrodes 8 b and 8 c are provided on an upper-side main surface of the dielectric layer 1 d. Further, four via electrodes 7 k through 7 n extend through both of the main surfaces of the dielectric layer 1 d. The capacitor electrode 8 b is connected to the via electrode 7 k and the capacitor electrode 8 c is connected to the via electrode 7 n. Further, the via electrode 7 k is connected to the other end of the line electrode 6 c, the via electrode 7 l is connected to the via electrode 7 g, the via electrode 7 m is connected to the via electrode 7 h, and the via electrode 7 n is connected to the other end of the line electrode 6 d.

A ground electrode 5 b is provided on an upper-side main surface of the dielectric layer 1 e. Further, four via electrodes 7 o through 7 r extend through both of the main surfaces of the dielectric layer 1 e. The ground electrode 5 b is connected to the via electrode 7 p and the via electrode 7 q. The via electrode 7 o is connected to the capacitor electrode 8 b, the via electrode 7 p is connected to the via electrode 7 l, the via electrode 7 q is connected to the via electrode 7 m, and the via electrode 7 r is connected to the capacitor electrode 8 c.

Capacitor electrodes 8 d and 8 e are provided on an upper-side main surface of the dielectric layer 1 f. In addition, five via electrodes 7 s through 7 w extend through both of the main surfaces of the dielectric layer 1 f. The via electrode 7 s is connected to the via electrode 7 o, three via electrodes 7 t, 7 u, and 7 v are all connected to the ground electrode 5 b, and the via electrode 7 w is connected to the via electrode 7 r.

Capacitor electrodes 8 f and 8 g are provided on an upper-side main surface of the dielectric layer 1 g. In addition, seven via electrodes 7 x through 7 ad extend through both of the main surfaces of the dielectric layer 1 g. The capacitor electrode 8 f is connected to the via electrode 7 x and the capacitor electrode 8 g is connected to the via electrode 7 ad. Further, the via electrode 7 x is connected to the via electrode 7 s, the via electrode 7 y is connected to the via electrode 7 t, the via electrode 7 z is connected to the capacitor electrode 8 d, the via electrode 7 aa is connected to the via electrode 7 u, the via electrode 1 ab is connected to the capacitor electrode 8 e, the via electrode 1 ac is connected to the via electrode 7 v, and the via electrode 7 ad is connected to the via electrode 7 w.

Four line electrodes 6 e through 6 h are provided on an upper-side main surface of the dielectric layer 1 h. Further, seven via electrodes 7 ae through 7 ak extend through both of the main surfaces of the dielectric layer 1 h. Then, one end of the line electrode 6 e is connected to the via electrode 7 ae, the other end of the line electrode 6 e is connected to the via electrode 7 af, one end of the line electrode 6 f is connected to the via electrode 7 ag, the other end of the line electrode 6 f is connected to the via electrode 7 ah, one end of the line electrode 6 g is connected to the via electrode 7 ai, the other end of the line electrode 6 g is connected to the via electrode 7 ah, one end of the line electrode 6 h is connected to the via electrode 7 ak, and the other end of the line electrode 6 h is connected to the via electrode 7 aj. Note that the other end of the line electrode 6 f and the other end of the line electrode 6 g are both connected to the via electrode 7 ah. The via electrode 7 ae is connected to the capacitor electrode 8 f, the via electrode 7 af is connected to the via electrode 7 y, the via electrode 7 ag is connected to the via electrode 7 z, the via electrode 7 ah is connected to the via electrode 7 aa, the via electrode 7 ai is connected to the via electrode 1 ab, the via electrode 7 aj is connected to the via electrode 1 ac, and the via electrode 7 ak is connected to the capacitor electrode 8 g.

On an upper-side main surface of the dielectric layer 1 i, four line electrodes 6 i through 6 l are provided. In addition, nine via electrodes 7 al through 7 at extend through both of the main surfaces of the dielectric layer 1 i. One end of the line electrode 6 i is connected to the via electrode 7 al, the other end of the line electrode 6 i is connected to the via electrode 7 am, one end of the line electrode 6 j is connected to the via electrode 7 ao, an intermediate portion of the line electrode 6 j is connected to the via electrode 7 an, the other end of the line electrode 6 j is connected to the via electrode 7 ap, one end of the line electrode 6 k is connected to the via electrode 7 aq, an intermediate portion of the line electrode 6 k is connected to the via electrode 7 ar, the other end of the line electrode 6 k is connected to the via electrode 7 ap, one end of the line electrode 6 l is connected to the via electrode 7 at, and the other end of the line electrode 6 l is connected to the via electrode 7 as. Note that the other end of the line electrode 6 j and the other end of the line electrode 6 k are both connected to the via electrode 7 ap. The via electrode 7 al is connected to the one end of the line electrode 6 e, the via electrode 7 am is connected to the other end of the line electrode 6 e, the via electrode 7 ao is connected to the one end of the line electrode 6 f, the via electrode 7 an is connected to an intermediate portion of the line electrode 6 f, the via electrode 7 ap is connected to the other end of the line electrode 6 f (this is also the other end of the line electrode 6 g), the via electrode 7 aq is connected to the one end of the line electrode 6 g, the via electrode 7 ar is connected to an intermediate portion of the line electrode 6 g, the via electrode 7 at is connected to the one end of the line electrode 6 h, and the via electrode 7 as is connected to the other end of the line electrode 6 h.

On an upper-side main surface of the dielectric layer 1 j, four line electrodes 6 m through 6 p are provided. Further, nine via electrodes 7 au through 7 bc extend through both of the main surfaces of the dielectric layer 1 j. One end of the line electrode 6 m is connected to the via electrode 7 au, the other end of the line electrode 6 m is connected to the via electrode 7 av, one end of the line electrode 6 n is connected to the via electrode 7 ax, an intermediate portion of the line electrode 6 n is connected to the via electrode 7 aw, the other end of the line electrode 6 n is connected to the via electrode 7 ay, one end of the line electrode 6 o is connected to the via electrode 7 az, an intermediate portion of the line electrode 6 o is connected to the via electrode 7 ba, the other end of the line electrode 6 o is connected to the via electrode 7 ay, one end of the line electrode 6 p is connected to the via electrode 7 bc, and the other end of the line electrode 6 p is connected to the via electrode 7 bb. Note that the other end of the line electrode 6 n and the other end of the line electrode 6 o are both connected to the via electrode 7 ay. The via electrode 7 au is connected to the one end of the line electrode 6 i, the via electrode 7 av is connected to the other end of the line electrode 6 i, the via electrode 7 ax is connected to the one end of the line electrode 6 j, the via electrode 7 aw is connected to the intermediate portion of the line electrode 6 j, the via electrode 7 ay is connected to the other end of the line electrode 6 j (this is also the other end of the line electrode 6 k), the via electrode 7 az is connected to the one end of the line electrode 6 k, the via electrode 7 ba is connected to the intermediate portion of the line electrode 6 k, the via electrode 7 bc is connected to the one end of the line electrode 6 l, and the via electrode 7 bb is connected to the other end of the line electrode 6 l.

The pair of input-output terminals 2 a and 2 b is provided on the end surfaces of the dielectric layer 1 k that oppose each other. In addition, the ground terminals 3 a and 3 b are provided on the side surfaces of the dielectric layer 1 k that oppose each other. One end of each of the input-output terminals 2 a, 2 b and the ground terminals 3 a, 3 b extends to an upper-side main surface of the dielectric layer 1 k.

As discussed above, in the laminated LC filter 100 according to the first preferred embodiment, the input-output terminals 2 a, 2 b and the ground terminals 3 a, 3 b are provided on the surface of the multilayer body 1. Inside the multilayer body 1, the connection electrodes 4 a and 4 b, the ground electrodes 5 a and 5 b, the line electrodes 6 a through 6 p, the via electrodes 7 a through 7 bc, and the capacitor electrodes 8 a through 8 g are provided.

A metal whose main component is Ag, Cu, or an alloy of these metals, for example, can preferably be used for the input-output terminals 2 a, 2 b and the ground terminals 3 a, 3 b. A plating layer whose main component is Ni, Sn, Au, or other suitable plating material, for example, may preferably be provided on the surface of the input-output terminals 2 a, 2 b and the ground terminals 3 a, 3 b as desired in either a single layer or a plurality of layers.

A metal whose main component is Ag, Cu, or an alloy of these metals, for example, can preferably be used for the connection electrodes 4 a and 4 b, the ground electrodes 5 a and 5 b, the line electrodes 6 a through 6 p, the via electrodes 7 a through 7 bc, and the capacitor electrodes 8 a through 8 g.

The laminated LC filter 100 according to the first preferred embodiment can be manufactured using a general manufacturing method having been used for the manufacture of laminated LC filters configured to include a multilayer body in which dielectric layers are laminated.

The laminated LC filter 100 having the above-described structure according to the first preferred embodiment has an equivalent circuit as shown in FIG. 2.

The laminated LC filter 100 is configured such that four LC parallel resonators Re1 through Re4 are inserted between the ground and a signal line connecting the input-output terminals 2 a and 2 b.

The first-stage LC parallel resonator Re1 includes an inductor L1 and a capacitor C1 connected in parallel.

The second-stage LC parallel resonator Re2 includes an inductor L2 and a capacitor C2 connected in parallel.

The third-stage LC parallel resonator Re3 includes an inductor L3 and a capacitor C3 connected in parallel.

The fourth-stage LC parallel resonator Re4 includes an inductor L4 and a capacitor C4 connected in parallel.

Note that the inductor L2 in the second-stage LC parallel resonator Re2 and the inductor L3 in the third-stage LC parallel resonator Re3 are connected to each other and then connected to the ground through a common inductor L23. The common inductor L23 can be considered to define a portion of the inductor L2 and also to define a portion of the inductor L3.

In the signal line connecting the input-output terminals 2 a and 2 b, an inductor L01 is provided between the input-output terminal 2 a and the first-stage LC parallel resonator Re1.

In the signal line connecting the input-output terminals 2 a and 2 b, a capacitor C12 is provided between the first-stage LC parallel resonator Re1 and the second-stage LC parallel resonator Re2.

In the signal line connecting the input-output terminals 2 a and 2 b, a capacitor C34 is provided between the third-stage LC parallel resonator Re3 and the fourth-stage LC parallel resonator Re4.

In the signal line connecting the input-output terminals 2 a and 2 b, an inductor L40 is provided between the fourth-stage LC parallel resonator Re4 and the input-output terminal 2 b.

A capacitor C14 is connected in parallel to a signal line connecting the capacitor C12, the second-stage LC parallel resonator Re2, the third-stage LC parallel resonator Re3, and the capacitor C34.

Next, a relationship between the structure and equivalent circuit of the laminated LC filter 100 will be described with reference to FIGS. 1 and 2.

As discussed in the “Description of the Related Art” above, in a laminated LC filter, in order to improve a Q value, line electrodes are configured to be multi-layered and to include a plurality of layers.

In the laminated LC filter 100, preferably, the one end of the line electrode 6 a and the one end of the line electrode 6 c are connected through the via electrode 7 f while the other ends thereof are connected through the via electrode 7 e, such that the line electrodes 6 a and 6 c are multi-layered and include two layers, for example.

Similarly, preferably, the one end of the line electrode 6 b and the one end of the line electrode 6 d are connected through the via electrode 7 d while the other ends thereof are connected through the via electrode 7 j, such the line electrodes 6 b and 6 d are multi-layered and include two layers, for example.

Further, preferably, the one ends of the line electrodes 6 e, 6 i, and 6 m are connected through the via electrodes 7 al and 7 au while the other ends thereof are connected through the via electrodes 7 an and 7 aw, such that the line electrodes 6 e, 6 i, and 6 m are multi-layered and include three layers, for example.

Similarly, preferably, the one ends of the line electrodes 6 f, 6 j, and 6 n are connected through the via electrodes 7 ao and 7 ax, the intermediate portions thereof are connected through the via electrodes 7 an and 7 aw, and the other ends thereof are connected through the via electrodes 7 ap and 7 ay, such that the line electrodes 6 f, 6 j, and 6 n are multi-layered and include three layers, for example.

Similarly, preferably, the one ends of the line electrodes 6 g, 6 k, and 6 o are connected through the via electrodes 7 aq and 7 az, the intermediate portions thereof are connected through the via electrodes 7 ar and 7 ba, and the other ends thereof are connected through the via electrodes 7 ap and 7 ay, such that the line electrodes 6 g, 6 k, and 6 o are multi-layered and include three layers, for example.

Similarly, preferably, the one ends of the line electrodes 6 h, 61, and 6 p are connected through the via electrodes 7 at and 7 bc while the other ends thereof are connected through the via electrodes 7 as and 7 bb, such that the line electrodes 6 h, 61, and 6 p are multi-layered and include three layers, for example.

The inductor L01 is defined by a path connecting the input-output terminal 2 a, the connection electrode 4 a, the via electrode 7 a, the line electrodes 6 a and 6 c connected through the via electrodes 7 e and 7 f, and the via electrode 7 k. The inductor L01 is structured to improve attenuation on a higher frequency side, for example, attenuation near a frequency of approximately 12 GHz in FIG. 3 to be explained later.

The capacitor C12 is primarily defined by a capacitance provided between the capacitor electrode 8 f and the capacitor electrode 8 d.

The capacitor C34 is primarily defined by a capacitance produced between the capacitor electrode 8 e and the capacitor electrode 8 g.

The inductor L40 is defined by a path connecting the via electrode 7 n, the line electrodes 6 b and 6 d connected through the via electrodes 7 i and 7 j, the via electrode 7 d, the connection electrode 4 b, and the input-output terminal 2 b. The inductor L40 is structured to improve attenuation on the higher frequency side.

The capacitor C14 is primarily defined by a capacitance produced by the capacitor electrode 8 b, the capacitor electrode 8 a as a floating electrode, and the capacitor electrode 8 c.

The inductor L1 in the first-stage LC parallel resonator Re1 is defined by a loop connecting a capacitor-side via electrode portion, a line electrode portion, and a ground-side via electrode portion.

The capacitor-side via electrode portion of the inductor L1 is defined by the via electrode 7 o connected to the capacitor electrode 8 b, the via electrode 7 s, the via electrode 7 x, the capacitor electrode 8 f, and the via electrode 7 ae.

The line electrode portion of the inductor L1 is defined by the line electrodes 6 e, 6 i, and 6 m connected in three layers through the via electrodes 7 al, 7 am, 7 au, and 7 av.

The ground-side via electrode portion of the inductor L1 is defined by the via electrode 7 af, the via electrode 7 y, and the via electrode 7 t connected to the ground electrode 5 b.

The capacitor C1 in the first-stage LC parallel resonator Re1 is primarily defined by a capacitance produced between the capacitor electrode 8 b and the ground electrode 5 b.

As discussed above, the inductor L1 and the capacitor C1 in the first-stage LC parallel resonator Re1 are preferably connected in parallel to each other.

The inductor L2 in the second-stage LC parallel resonator Re2 and the common inductor L23 are defined by a loop connecting a capacitor-side via electrode portion, a line electrode portion, and a ground-side via electrode portion. As discussed above, the common inductor L23 can be considered to defined a portion of the inductor L2.

The capacitor-side via electrode portion of the inductor L2 is defined by the via electrode 7 z connected to the capacitor electrode 8 d and the via electrode 7 ag.

The line electrode portion of the inductor L2 is defined by the line electrodes 6 f, 6 j, and 6 n connected in three layers through the via electrodes 7 an, 7 ao, 7 ap, 7 aw, 7 ax, and 7 ay.

The ground-side via electrode portion of the inductor L2 is defined by the via electrodes 7 ah and 7 aa, and the via electrode 7 u connected to the ground electrode 5 b.

The capacitor C2 in the second-stage LC parallel resonator Re2 is primarily defined by a capacitance produced between the capacitor electrode 8 d and the ground electrode 5 b.

As discussed above, the inductor L2 and the capacitor C2 in the second-stage LC parallel resonator Re2 are preferably connected in parallel to each other.

The inductor L3 in the third-stage LC parallel resonator Re3 and the common inductor L23 are defined by a loop connecting a capacitor-side via electrode portion, a line electrode portion, and a ground-side via electrode portion. As discussed above, the common inductor L23 can be considered to defined a portion of the inductor L3.

The capacitor-side via electrode portion of the inductor L3 is defined by the via electrode 1 ab connected to the capacitor electrode 8 e, and the via electrode 7 ai.

The line electrode portion of the inductor L3 is defined by the line electrodes 6 f, 6 j, and 6 n connected in three layers through the via electrodes 7 ap, 7 aq, 7 ar, 7 ay, 7 az, and 7 ba.

The ground-side via electrode portion of the inductor L3 is defined by the via electrodes 7 ah and 7 aa, and the via electrode 7 u connected to the ground electrode 5 b.

The capacitor C3 in the third-stage LC parallel resonator Re3 is primarily defined by a capacitance produced between the capacitor electrode 8 e and the ground electrode 5 b.

As discussed above, the inductor L3 and the capacitor C3 in the third-stage LC parallel resonator Re3 are preferably connected in parallel to each other.

The inductor L4 in the fourth-stage LC parallel resonator Re4 is defined by a loop connecting a capacitor-side via electrode portion, a line electrode portion, and a ground-side via electrode portion.

The capacitor-side via electrode portion of the inductor L4 is defined by the via electrode 7 r connected to the capacitor electrode 8 c, the via electrode 7 w, the via electrode 7 ad, (capacitor electrode 8 g), and the via electrode 7 ak.

The line electrode portion of the inductor L4 is defined by the line electrodes 6 h, 61, and 6 p connected in three layers through the via electrodes 7 as, 7 at, 7 bb, and 7 bc.

The ground-side via electrode portion of the inductor L4 is defined by the via electrode 7 aj, the via electrode 1 ac, and the via electrode 7 v connected to the ground electrode 5 b.

The capacitor C4 in the fourth-stage LC parallel resonator Re4 is primarily defined by a capacitance produced between the capacitor electrode 8 c and the ground electrode 5 b.

As discussed above, the inductor L4 and the capacitor C4 in the fourth-stage LC parallel resonator Re4 are preferably connected in parallel to each other.

In the laminated LC filter 100 according to the present preferred embodiment, the first-stage LC parallel resonator Re1 and the second-stage LC parallel resonator Re2 are primarily capacitively coupled to one another through the capacitor C12.

Further, in the laminated LC filter 100, the second-stage LC parallel resonator Re2 and the third-stage LC parallel resonators Re3 are coupled primarily through magnetic coupling between the inductor L2 and inductor L3 because the ground-side via electrode portion of the inductor L2 and the ground-side via electrode portion of the inductor L3 are integrated by the common inductor L23.

Although the winding directions of the loop of the inductor L2 and the loop of the inductor L3 are different from each other, the inductors L2 and L3 are coupled to each other by magnetic coupling M23 because both of the ground-side via electrode portions thereof are integrated by the common inductor L23.

This configuration is also used in the laminated LC filter 1100 disclosed in International Publication No. WO 2012/077498, as shown in FIGS. 7 through 9. However, the magnetic coupling between the inductors L2 and L3 in the laminated LC filter 100 of the present preferred embodiment is significantly stronger than that in the laminated LC filter 1100 of International Publication No. WO 2012/077498.

In the laminated LC filter 1100 disclosed in International Publication No. WO 2012/077498, as shown in FIG. 7, the line electrode 106 f defining the inductor L2 and the line electrode 106 g defining the inductor L3 are not connected to one another, and the line electrode 106 j defining the inductor L2 and the line electrode 106 k defining inductor L3 are also not connected to one another, but the line electrode 106 c defining the inductor L2 and the line electrode 106 d defining the inductor L3 are connected at a position closer to the ground electrode 104 c, and then connected to the ground electrode 104 c through the common inductor L23 defined by the via electrodes 105 bb, 105 av, 105 aq, 105 ak, and 105 ae. Accordingly, in the laminated LC filter 1100, the inductors L2 and L3 are not integrated to be common to the maximum extent possible, and the strength of the magnetic coupling between the inductors L2 and L3 is relatively weak as compared to the structure of the present preferred embodiment.

In contrast, in the laminated LC filter 100 according to the present preferred embodiment, the line electrode portion of the inductor L2 that is defined by the line electrodes 6 f, 6 j, and 6 n connected in three layers through the via electrodes 7 an, 7 ao, 7 ap, 7 aw, 7 ax, and 7 ay, and the line electrode portion of the inductor L3 that is defined by the line electrodes 6 g, 6 k, and 6 o connected in three layers through the via electrodes 7 ap, 7 aq, 7 ar, 7 ay, 7 az, and 7 ba are connected, and then connected to the ground electrode 5 b through the common inductor L23 defined by the via electrodes 7 ah, 7 aa, and 7 u.

That is, in the laminated LC filter 100, the inductor L2 and the inductor L3 are preferably connected at the line electrode portions thereof, and the ground-side via electrode portion of the inductor L2 and the ground-side via electrode portion of the inductor L3 are completely integrated by the common inductor L23. In other words, in the laminated LC filter 100, the inductor L2 and the inductor L3 are integrated to be common to the maximum extent possible so that the magnetic coupling between the inductor L2 and the inductor L3 is significantly stronger as compared to the laminated LC filter 1100 disclosed International Publication No. WO 2012/077498.

In the laminated LC filter 100, since the magnetic coupling between the inductors L2 and L3 is strengthened to the maximum extent possible, the pass band thereof is further widened.

Further, in the laminated LC filter 100, the third-stage LC parallel resonator Re3 and the fourth-stage LC parallel resonator Re4 are preferably primarily capacitively coupled through the capacitor C34.

Furthermore, in the laminated LC filter 100, the first-stage LC parallel resonator Re1 and the fourth-stage LC parallel resonator Re4 are primarily capacitively coupled through the capacitor C14.

Moreover, with the structure of the laminated LC filter 100 according to the present preferred embodiment of the present invention, the inductor L1 in the first-stage LC parallel resonator Re1 and the inductor L3 in the third-stage LC parallel resonator Re3 are coupled by magnetic coupling M13, and the inductor L2 in the second-stage LC parallel resonator Re2 and the inductor L4 in the fourth-stage LC parallel resonator Re4 are coupled by magnetic coupling M24.

That is, because the loop of the inductor L1 in the first-stage LC parallel resonator Re1 and the loop of the inductor L3 in the third-stage LC parallel resonator Re3 are disposed at an angle at which magnetic coupling is obtained, and the winding directions thereof are the same, the inductor L1 and the inductor L3 are coupled by the magnetic coupling M13.

Further, because the loop of the inductor L2 in the second-stage LC parallel resonator Re2 and the loop of the inductor L4 in the fourth-stage LC parallel resonator Re4 are disposed at an angle at which magnetic coupling is obtained, and the winding directions thereof are the same, the inductor L2 and the inductor L4 are coupled by the magnetic coupling M24.

In the laminated LC filter 100 according to the present preferred embodiment, the inductor L1 in the first-stage LC parallel resonator Re1 and the inductor L3 in the third-stage LC parallel resonator Re3 are coupled by the magnetic coupling M13, and the inductor L2 in the second-stage LC parallel resonator Re2 and the inductor L4 in the fourth-stage LC parallel resonator Re4 are coupled by the magnetic coupling M24, such that an attenuation pole having sufficient attenuation is provided near the pass band and high attenuation characteristics are achieved.

FIG. 3 illustrates frequency characteristics of the laminated LC filter 100 according to the present preferred embodiment. Note that a solid line indicates a bandpass characteristic while a broken line indicates a reflection characteristic.

As is understood from FIG. 3, the laminated LC filter 100 has a wide pass band. As described above, causing the inductor L2 in the second-stage LC parallel resonator Re2 and the inductor L3 in the third-stage LC parallel resonator Re3 to be strongly coupled by the magnetic coupling M23 contributes to the widening of the pass band.

As is also understood from FIG. 3, in the laminated LC filter 100, an attenuation pole having sufficient attenuation is provided near the pass band so that high attenuation characteristics are achieved. As described above, causing the inductor L1 in the first-stage LC parallel resonator Re1 and the inductor L3 in the third-stage LC parallel resonator Re3 to be coupled by the magnetic coupling M13 and causing the inductor L2 in the second-stage LC parallel resonator Re2 and the inductor L4 in the fourth-stage LC parallel resonator Re4 to be coupled by the magnetic coupling M24 contribute to the attenuation pole being provided near the pass band.

The laminated LC filter 100 according to the present preferred embodiment has excellent frequency characteristics.

Second Preferred Embodiment

FIG. 4 illustrates a laminated LC filter 200 according to a second preferred embodiment of the present invention.

FIG. 4 is an exploded perspective view illustrating a main portion of the laminated LC filter 200. It is to be noted that the laminated LC filter 100 according to the first preferred embodiment is also illustrated in FIG. 4 for comparison.

In the laminated LC filter 200, the via electrodes 7 an, 7 ar, 7 aw, and 7 ba are preferably removed from the laminated LC filter 100 according to the first preferred embodiment.

That is, in the laminated LC filter 100, when the line electrode portion of the inductor L2 in the second-stage LC parallel resonator Re2 includes three layers of the line electrodes 6 f, 6 j, and 6 n, each one end of the line electrodes is connected through the via electrodes 7 ao and 7 ax, each intermediate portion thereof is connected through the via electrodes 7 an and 7 aw, and each other end thereof is connected through the via electrodes 7 ap and 7 ay. However, in the laminated LC filter 200, the connections of the intermediate portions through the via electrodes 7 an and 7 aw are preferably removed.

Similarly, in the laminated LC filter 100, when the line electrode portion of the inductor L3 in the third-stage LC parallel resonator Re3 includes three layers of the line electrodes 6 g, 6 k, and 6 o, each one end of the line electrodes is connected through the via electrodes 7 aq and 7 az, each intermediate portion thereof is connected through the via electrodes 7 ar and 7 ba, and each other end thereof is connected through the via electrodes lap and 7 ay. However, in the laminated LC filter 200, the connections of the intermediate portions through the via electrodes 7 ar and 7 ba are removed.

In the laminated LC filter 200, although the via electrodes 7 an, 7 ar, 7 aw, and 7 ba are removed, any change in frequency characteristics is not observed as compared to the laminated LC filter 100. As such, as in the laminated LC filter 100, an attenuation pole having sufficient attenuation is provided near the pass band while maintaining a wide band, thereby achieving the high attenuation characteristics.

Third Preferred Embodiment

FIG. 5 illustrates a laminated LC filter 300 according to a third preferred embodiment of the present invention.

FIG. 5 is an exploded perspective view illustrating a main portion of the laminated LC filter 300. It is to be noted that the laminated LC filter 100 according to the first preferred embodiment is also illustrated in FIG. 5 for comparison.

In the laminated LC filter 300, as in the laminated LC filter 200 according to the second preferred embodiment, the via electrodes 7 an, 7 ar, 7 aw, and 7 ba are preferably removed from the laminated LC filter 100 according to the first preferred embodiment.

Further, in the laminated LC filter 300, the shapes of the line electrodes 6 f, 6 j, and 6 n defining the line electrode portion of the inductor L2 in the second-stage LC parallel resonator Re2 and the shapes of the line electrodes 6 g, 6 k, and 6 o defining the line electrode portion of the inductor L3 in the third-stage LC parallel resonator Re3 are preferably modified.

More specifically, preferably, the line electrode 6 f and the line electrode 6 g are integrated so as to be a single entity, such as a line electrode 16 fg that has a rectangular or substantially rectangular shape and a large surface area, for example.

Similarly, preferably. the line electrode 6 j and the line electrode 6 k are integrated so as to be a single entity, such as a line electrode 16 jk that has a rectangular or substantially rectangular shape and a large surface area, for example.

Similarly, preferably, the line electrode 6 n and the line electrode 6 o are integrated so as to be a single entity, such as a line electrode 16 no that has a rectangular or substantially rectangular shape and a large surface area, for example.

In the laminated LC filter 300, with the removal of the above-described via electrodes and the modification of the shapes of the above-described line electrodes, the shapes of the capacitor electrodes 8 a, 8 d, 8 e, 8 f, and 8 g are also modified in order to adjust the frequency characteristics.

As shown in FIG. 5, the shape of the capacitor electrode 8 d is preferably modified so as to have the shape of a capacitor electrode 18 d, the shape of the capacitor electrode 8 e is modified so as to have the shape of a capacitor electrode 18 e, the shape of the capacitor electrode 8 f is modified so as to have the shape of a capacitor electrode 18 f, and the shape of the capacitor electrode 8 g is modified so as to have the shape of a capacitor electrode 18 g. Note that in FIG. 5, because the dielectric layer 1 c on which the capacitor electrode 8 a is provided is not illustrated, the capacitor electrode 8 a with its shape having been modified is also not illustrated.

In the laminated LC filter 300, preferably, some of the via electrodes are removed and the shapes of some of the line electrodes and capacitor electrodes are modified as compared to the laminated LC filter 100 according to the first preferred embodiment. However, the laminated LC filter 300 exhibits excellent frequency characteristics similarly to the laminated LC filter 100.

Fourth Preferred Embodiment

A laminated LC filter 400 according to a fourth preferred embodiment of the present invention is shown in FIG. 6.

FIG. 6 is an exploded perspective view of the laminated LC filter 400.

In the laminated LC filter 400, the dielectric layers 1 i and 1 j are removed, together with the via electrodes and the line electrodes provided on the two dielectric layers 1 i and 1 j, from the laminated LC filter 100 according to the first preferred embodiment, and then the dielectric layer 1 k is laminated on the dielectric layer 1 h.

That is, although the line electrode portion of the inductor L1 in the first-stage LC parallel resonator Re1 is defined by the line electrodes 6 e, 6 i, and 6 m including three layers in the laminated LC filter 100 according to the first preferred embodiment, the line electrode portion of the inductor L1 in the laminated LC filter 400 is preferably defined by the line electrode 6 e including a single layer.

Similarly, although the line electrode portion of the inductor L2 in the second-stage LC parallel resonator Re2 is defined by the line electrodes 6 f, 6 j, and 6 n including three layers in the laminated LC filter 100, the line electrode portion of the inductor L2 in the laminated LC filter 400 is preferably defined by the line electrode 6 f including a single layer.

Similarly, although the line electrode portion of the inductor L3 in the third-stage LC parallel resonator Re3 is defined by the line electrodes 6 g, 6 k, and 6 o including three layers in the laminated LC filter 100, the line electrode portion of the inductor L3 in the laminated LC filter 400 is preferably defined by the line electrode 6 g including a single layer.

Similarly, although the line electrode portion of the inductor L4 in the fourth-stage LC parallel resonator Re4 is defined by the line electrodes 6 h, 61, and 6 p including three layers in the laminated LC filter 100, the line electrode portion of the inductor L4 in the laminated LC filter 400 is preferably defined by the line electrode 6 h including a single layer.

Although the multi-layer structure of the line electrode portions of the inductors contributes to lowering resistance and improving a Q value, such a multi-layer structure is not necessary in preferred embodiments of the present invention. Alternatively, as in the laminated LC filter 400, each line electrode portion can be defined by a line electrode including a single layer.

The laminated LC filters 100 through 400 according to the first through fourth preferred embodiments of the present invention, respectively, have been discussed. However, the present invention is not limited thereto, and various modifications can be made within the scope and spirit of the present invention.

For example, although each of the laminated LC filters 100 through 400 preferably is a four-stage laminated LC filter including the four LC parallel resonators Re1 through Re4, the number of stages is not limited to four.

For example, the filter may be a five-stage laminated LC filter including five LC parallel resonators Re1 through Re5, a six-stage laminated LC filter including six LC parallel resonators Re1 through Re6, or a multi-stage laminated LC filter including six or more LC parallel resonators.

Further, at least a pair of inductor loops in odd numbered-stage LC parallel resonators, which are disposed at an angle at which magnetic coupling is obtained therebetween and the winding directions of which are the same, refers to the loops of the inductors in the first-stage and third-stage LC parallel resonators in any of the laminated LC filters 100 through 400. However, the combination of inductor loops is not limited thereto.

For example, the loops of inductors in the first-stage, third-stage, and fifth-stage LC parallel resonators may be combined. Alternatively, the loops of inductors in the third-stage and fifth-stage LC parallel resonators may be combined.

Further, the number of layers, shapes, materials, and other structural features of the dielectric layers as well as the number, shapes, materials, and other structural features of the line electrodes, capacitor electrodes, ground electrodes, via electrodes, and other elements are not limited to the aforementioned examples, and can be arbitrarily determined.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. A laminated LC filter comprising: a multilayer body including a plurality of dielectric layers that are laminated; a plurality of line electrodes disposed between respective layers of the plurality of dielectric layers; a plurality of capacitor electrodes disposed between respective layers of the plurality of dielectric layers; at least one ground electrode disposed between respective layers of the plurality of dielectric layers; and a plurality of via electrodes extending through two main surfaces of respective layers of the plurality of dielectric layers; wherein the laminated LC filter includes at least four LC parallel resonators inside the multilayer body and has a predetermined pass band; an inductor and a capacitor are connected in parallel in each of the at least four LC parallel resonators; the inductor of each of the at least four LC parallel resonators includes: a capacitor-side via electrode portion which is defined by at least one of the plurality of via electrodes and one end of which is connected to one of the plurality of capacitor electrodes, a line electrode portion which is defined by at least one of the plurality of line electrodes and one end of which is connected to another end of the capacitor-side via electrode portion, and a ground-side via electrode portion which is defined by at least one of the plurality of via electrodes, one end of the ground-side via electrode portion is connected to another end of the line electrode portion, and another end of the ground-side via electrode portion is connected to the at least one ground electrode; the inductor of each of the at least four LC parallel resonators includes a loop with a predetermined winding direction and connecting the capacitor-side via electrode portion, the line electrode portion, and the ground-side via electrode portion to each other; the capacitor of each of the at least four LC parallel resonators is defined by a capacitance produced between one of the plurality of capacitor electrodes and the ground electrode or a capacitance produced among the plurality of capacitor electrodes; the loops of the inductors of a pair of the LC parallel resonators among the at least four LC parallel resonators are disposed at an angle at which magnetic coupling is obtained between each other, and winding directions of the loops of the inductors are the same; the at least four LC parallel resonators include at least a first-stage LC parallel resonator, a second-stage LC parallel resonator, a third-stage LC parallel resonator, and a fourth-stage LC parallel resonator; the loops of the inductors which are disposed at the angle at which magnetic coupling is obtained between each other and whose winding directions are the same define the loop of the inductor in the first-stage LC parallel resonator and the loop of the inductor in the third-stage LC parallel resonator, or the loop of the inductor in the second-stage LC parallel resonator and the loop of the inductor in the fourth-stage LC parallel resonator; the winding direction of the loop of the inductor in the second-stage LC parallel resonator and the winding direction of the loop of the inductor in the third-stage LC parallel resonator are different from each other; the ground-side via electrode portion of the inductor in the second-stage LC parallel resonator and the ground-side via electrode portion of the inductor in the third-stage LC parallel resonator are integrated to define a common ground-side via portion; the common ground-side via portion is connected to the at least one ground electrode; and one end of the common ground-side via portion is directly connected to the another end of the line electrode portion of each of the second-stage LC parallel resonator and the third-stage LC parallel resonator, and another end of the common ground-side via portion is connected to the at least one ground electrode.
 2. The laminated LC filter according to claim 1, wherein the loops which are disposed at the angle at which magnetic coupling is obtained between each other and whose winding directions are the same define the loop of the inductor in the first-stage resonator and the loop of the inductor in the third-stage LC parallel resonator, and the loop of the inductor in the second-stage LC parallel resonator and the loop of the inductor in the fourth stage LC parallel resonator.
 3. The laminated LC filter according to claim 1, wherein the first-stage LC parallel resonator and the fourth-stage LC parallel resonator are primarily coupled to one another through capacitive coupling.
 4. The laminated LC filter according to claim 1, wherein the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator are single-layered line electrode portions; and the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator are directly connected.
 5. The laminated LC filter according to claim 1, wherein each of the plurality of dielectric layers is made of a ceramic material.
 6. The laminated LC filter according to claim 1, wherein a pair of input-output terminals are provided on opposing end surfaces of at least one layer of the plurality of dielectric layers, and a pair of ground terminals are provided on opposing side surfaces of the at least one layer of the plurality of dielectric layers.
 7. The laminated LC filter according to claim 6, wherein a pair of connection electrodes and a second ground electrode are provided on an upper-side main surface of the at least one layer of the plurality of dielectric layers; the pair of connection electrodes are respectively connected to the pair of input-output terminals; and the second ground electrode is connected to both of the pair of ground terminals.
 8. The laminated LC filter according to claim 6, wherein the pair of input-output terminals are also provided on opposing end surfaces of all of the plurality of dielectric layers, and the pair of ground terminals are provided on opposing side surfaces of all of the plurality of dielectric layers.
 9. The laminated LC filter according to claim 6, wherein the pair of input-output terminals and the pair of ground terminals include Ag, Cu, or an alloy of Ag and Cu as a main component.
 10. The laminated LC filter according to claim 9, wherein each of the pair of input-output terminals and the pair of ground terminals include a plating layer that includes Ni, Sn, or Au as a main component.
 11. The laminated LC filter according to claim 1, wherein the third-stage LC parallel resonator and the fourth-stage LC parallel resonator are primarily coupled to one another through capacitive coupling.
 12. The laminated LC filter according to claim 1, wherein the first-stage LC parallel resonator and the second-stage LC parallel resonator are primarily coupled to one another through capacitive coupling.
 13. The laminated LC filter according to claim 1, wherein the second-stage LC parallel resonator and the third-stage LC parallel resonator are primarily coupled to one another through magnetic coupling.
 14. The laminated LC filter according to claim 1, wherein the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator are each multi-layered and include a plurality of layers of the line electrode portion; and the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator are directly connected.
 15. The laminated LC filter according to claim 14, wherein each of the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator includes two layers of the line electrode portion; and one end of each of the two layers of the line electrode portion are connected through a first one of the plurality of via electrodes, and another end of each of the two layers of the line electrode portion are connected through a second one of the plurality of via electrodes.
 16. The laminated LC filter according to claim 14, wherein each of the line electrode portion of the inductor in the second-stage LC parallel resonator and the line electrode portion of the inductor in the third-stage LC parallel resonator includes three layers of the line electrode portion; and one end of each of the three layers of the line electrode portion are connected to each other through first and second via electrodes of the plurality of via electrodes, and another end of each of the three layers of the line electrode portion are connected to each other through third and fourth via electrodes of the plurality of via electrodes. 